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Faecal nematode egg counts in lactating ewes from Romney flocks selectively bred for divergence in lamb faecal egg count

Published online by Cambridge University Press:  02 September 2010

C. A. Morris ,
S. A. Bisset ,
A. Vlassoff ,
C. J. West  and
M. Wheeler
C. A. Morris
Affiliation:
1AgResearch, Ruakura Agricultural Research Centre, Private Bag 3123, Hamilton, New Zealand
S. A. Bisset
Affiliation:
2AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand
A. Vlassoff
Affiliation:
2AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand
C. J. West
Affiliation:
2AgResearch, Wallaceville Animal Research Centre, PO Box 40063, Upper Hutt, New Zealand
M. Wheeler
Affiliation:
1AgResearch, Ruakura Agricultural Research Centre, Private Bag 3123, Hamilton, New Zealand
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Abstract

Faecal nematode egg counts (FECs) were examined in lactating ewes from divergent flocks of Romney sheep which had been selectively bred from 1979 to 1996 for or against FEC in 4 to 7 month old lambs. Faecal samples were obtained from the ewes while under normal grazing management, 1 to 2 months after lambing in spring for each of 6 years between 1987 and 1996 (no. = 785 records; 298 animals). Analyses were carried out on loge (FEC + 100)–transformed data using animal-model maximum likelihood procedures, accounting for repeated records on ewes, within and between lactations. An examination of non-genetic effects indicated that there was no significant effect of age class of ewe on FEC but ewes which gave birth to single lambs had significantly lower post-parturient FECs than those bearing twins (back-transformed means of 184 v. 276 egg per g, respectively; P < 0·001). In relation to genetic effects, post-parturient FECs were significantly lower in ewes from the flock bred for low lamb-FEC than in their counterparts from the flock bred for high lamb-FEC, with ewes from the most recent birth years (1991 to 1994) showing a nine-fold difference (back-transformed means of 33 and 305 eggs per g faeces respectively; P < 0·001). This was equivalent to 69% of the divergence observed between loge (FEC + 100) in their lambs in the same years. Heritability and repeatability estimates for loge (FEC + 100) in ewes were 0·37 (s.e. 0·06) and 0·46 (s.e. 0·03) respectively. Genetic correlation estimates between a ewe's post-parturient loge (FEC + 200) and her loge (FEC + 100) as a lamb, based on analysis of (co)variance or realized responses, were 0·70 or 0·58 respectively. The phenotypic correlation between a ewe's loge (FEC + 100) and that of her lamb(s) in the same lactation was 0·29 (s.e. 0·06) (P < 0·001). From the results it is clear that substantial genetic changes in post-parturient FECs of breeding ewes can be induced through a correlated response to selective breeding for or against reduced FEC in lambs. This may have important implications for the epidemiology of nematode parasite infections in spring-born lambs, a possibility which is currently being investigated.

Keywords

disease resistancefaecal egg countparasitic nematodesselectionsheep
Type
Research Article
Information
Animal Science , Volume 67 , Issue 2 , October 1998 , pp. 283 - 288
Copyright
Copyright © British Society of Animal Science 1998

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References

Baker, R. L., Watson, T. G., Bisset, S. A. and Vlassoff, A. 1990. Breeding Romney sheep which are resistant to gastro-intestinal parasites. Proceedings of the Australian Association of Animal Breeding and Genetics 8:173–178.Google Scholar
Bisset, S. A., Vlassoff, A., Douch, P. G. C., Jonas, W. E., West, C. J. and Green, R. S. 1996. Nematode burdens and immunological responses following natural challenge in Romney lambs selectively bred for low or high faecal worm egg count. Veterinary Parasitology 61:249–263.CrossRefGoogle ScholarPubMed
Bisset, S. A., Vlassoff, A., Morris, C. A., Southey, B. R. and Baker, R. L. 1992. Heritability of and genetic correlations among faecal egg counts and productivity traits in Romney sheep. New Zealand Journal of Agricultural Research 35:51–58.CrossRefGoogle Scholar
Bisset, S. A., Vlassoff, A., West, C. J. and Morrison, L. 1997. Epidemiology of nematodosis in Romney lambs selectively bred for resistance or susceptibility to nematode infection. Veterinary Parasitology 70: 255–269.CrossRefGoogle ScholarPubMed
Brunsdon, R. V. 1980. Principles of helminth control. Veterinary Parasitology 6:185–215.CrossRefGoogle Scholar
Brunsdon, R. V. and Vlassoff, A. 1971. The post-parturient rise: a comparison of the pattern and relative generic composition of faecal strongyle egg counts in ewes and wethers. New Zealand Veterinary Journal 19:32–37.CrossRefGoogle Scholar
Courtney, C. H., Parker, C. F., McClure, K. E. and Herd, R. P. 1984. A comparison of the periparturient rise in fecal egg counts of exotic and domestic ewes. International Journal for Parasitology 14:377–381.CrossRefGoogle ScholarPubMed
Genstat. 1994. Statistical package: Genstat 5, release 3.1. Lawes Agricultural Trust, Rothamsted Experimental Station, UK.Google Scholar
Gilmour, A. R. 1997. ASREML for testing fixed effects and estimating multiple trait variance components. Proceedings of the Association for the Advancement of Animal Breeding and Genetics 12:386–390.Google Scholar
Johnson, D. L. and Thompson, R. 1995. Restricted maximum likelihood estimation of variance components for univariate animal models using sparse matrix techniques and average information. Journal of Dairy Science 78: 449–456.CrossRefGoogle Scholar
Morris, C. A., Bisset, S. A., Baker, R. L., Watson, T. G., Johnson, D. L. and Wheeler, M. 1993a. An investigation of sire by location interactions for faecal nematode egg counts in lambs. Proceedings of the New Zealand Society of Animal Production 53: 231–233.Google Scholar
Morris, C. A., Vlassoff, A., Bisset, S. A., Baker, R. L. and Watson, T. G. 1997a. Direct responses to selection for divergence in faecal nematode egg count in young Romney and Perendale sheep. Proceedings of the Association for the Advancement of Animal Breeding and Genetics 12:413–416.Google Scholar
Morris, C. A., Vlassoff, A., Bisset, S. A., Baker, R. L., West, C. J. and Hurford, A. P. 1997b. Responses of Romney sheep to selection for resistance or susceptibility to nematode infection. Animal Science 64:319–329.CrossRefGoogle Scholar
Morris, C. A., Watson, T. G., Baker, R. L., Hurford, A. P. and Hosking, B. C. 1993b. Repeatability estimates and selection flock effects for faecal nematode egg counts in Romney breeding ewes. Proceedings of the New Zealand Society of Animal Production 53:227–229.Google Scholar
Vlassoff, A. 1976. Seasonal incidence of infective trichostrongyle larvae on pasture: the contribution of the ewe and the role of residual pasture infestation as sources of infection to the lamb. New Zealand Journal of Experimental Agriculture 1:293–301.CrossRefGoogle Scholar
Watson, T. G., Hosking, B. C., Hurford, A. P. and Mather, B. C. 1992. Developments in breeding Perendale sheep for resistance or susceptibility to internal nematode parasites. Proceedings of the New Zealand Society of Animal Production 52: 61–64.Google Scholar
Watson, T. G., Hosking, B. C., Morris, C. A. and Hurford, A. P. 1995. Faecal nematode egg counts and haematology in Perendale ewes near lambing. Proceedings of the New Zealand Society of Animal Production 55:202–204.Google Scholar
Whitlock, H. V. 1948. Some modifications of the McMaster helminth egg-counting technique and apparatus. Journal of the Council for Scientific and Industrial Research 21:177–180.Google Scholar
Woolaston, R. R. 1992. Selection of Merino sheep for increased and decreased resistance to Haemonchus contortus: peri-parturient effects on faecal egg counts. International Journal for Parasitology 22: 947–953.CrossRefGoogle ScholarPubMed